Operating slide-valves fob steam-engines



' NTTED STATES PATENT OFFICE.

JOHN F. ALLEN, OF NEW YORK,

N. Y., ASSIGNOR TO N. L. COLE, OF NORWICH, CONNECTICUT.

OPERATING SLIDE-VALVES FOR STEAM-ENGINES.

Specification of Letters Patent No. 14,991, dated May 27, 1856.

To all whom t may concern.'

Be it known that I, JOHN F. ALLEN, of the city, county, and State of NewYork, have invented a new and useful appendage to be employed inconnection with the slidevalve of the steam-engine to prevent thecushioning of the steam in the cylinder on the exhaust side of thepiston; and I do hereby declare that the following is a full, clear, andexact description of the same, reference being had to the accompanyingdrawing, forming part of this specification, which represents alongitudinal section in a plane perpendicular to the valve-seat of asteam-chest and slide-valve of a locomotive-engine, showing also myappendage applied.

This invention consists in a movable valve seatarranged and applied tooperate as hereinafter described, between the face of the slide valveand t-he usual stationary seat, to obtain a free exhaust of steam to thetermination of the stroke of the piston or till the lead of the valvefor the induction of steam commences, thereby obviating the resistancewhich is caused by what is known to engineers as the cushioning of thesteam in the cylinders. The invention is applicable with especialadvantage when a lap valve is employed, as with that kind of a valve theexhausting port is generally entirely closed some time before the strokeof the piston terminates.

To enable others skilled in the art to make and use my invention, I willproceed to describe its construction and operation.

A, is the steam chest.

B, B, is the usual stationary valve seat with the usual arrangement ofsteam ports, a, a, and exhaust port, b.

C, is the slide valve, which is what is termed a lap valve.

D, is the valve stem.

E, is the movable valve seat which constitutes the subject of myinvention. This consists of a plate of metal which may be of a thicknessabout equal to the width of the ports, a, a, and is faced parallel onboth sides to fit between the valve C, and stationary seat, B. This seatis provided with ports, a, a*, and 6*, extending through it. The port,5*, which is in the center of the movable seat, is of precisely the samesize as the port, b. The ports, af, ai, are of such width and soarranged that when the port, 5*, is over the port b, in the fixed seatB, B, as shown in black outline, the inner edges ei, ci, of the saidparts of, ah, in the lower face of the movable seat just meet the inneredges, e, e, of the ports, a, and lthe outer edges if, if, thereof inthe upper face of the movable seat stand exactly opposite the outeredges i, z', of the ports, a, a, but from the edges, 6*, 0*, and 715,z'i, the sides of the ports, af, a, are beveled to increase their width.

The movable seat is furnished with a stem, E, which works through thesame end of the steam chest as the valve stem, D, and should be fittedwith a suitable stuffing box. This stem is fitted with two lightcollars, c, c', and with two loose yokes, d, d', and two spiral springs,f, f, are coiled around it between the two yokes, d, a?, and two fixedguides, g, g, through which the rod, F, works. These springs, f, f, actin opposite directions to force the yokes into contact with the collarsc, 0, and two fixed stops, Z, Z, are provided to stop the yokes in sucha position, shown in black outline, that when the stem, F, is not underany other influence, they hold it in such a position as to keep themovable seat with its ports opposite the ports of the fixed seat, asshown in black outline. The stem, F, is also provided with a stud, 71 onone side, which fits to a slot in a rocker, G, which is arranged to rockon a fixed pin lo. The valve stem, D, has a wiper, I, rigidly attachedto it in such a position that as the valve is moved in the common wayfor the induction and eduction of steam, the said wiper at every strokeof the valve in either direction wipes against the end of the rocker, G,and by that means, through the action. of the rocker on the stud L, inthe stem, F, moves the seat, E, along with the valve, and then passesthe said rocker and allows the seat to be returned by the action of thesprings, to the central position shown in black outline. T he eect ofthis movement of the seat, E, is to keep up a wide communication betweenthe exhaust cavity, m, of the valve and the port, a, or a, as the casemay require, through the port (1*, or af, and thus provide for a freeexhaust till the end of the stroke of the piston or till the valvebegins to take a lead to reverse the stroke, and then to let the seat,E, fly back to its central position for the induction of steam to thatend of the cylinder which has been exhausting.

The above operation is illustrated by the different positions of thevalve-and movable seat represented in the drawing, and by the aid ofthese positions I will endeavor to make it intelligible. Suppose, first,the valve to be at one end of its travel, as shown in black outline; themovable seat is in its central position with its ports exactly overthose of the stationary seat, and the eduction of steam takes placethrough the port, 06k, and eduction through the port, am, the same as itwould through the ports, a, a', if the movable valve seat were notthere. The valve now commences to move to the right and after havingmoved far enough to close the port, 'a*, to cut of the steam from theinduction side of the piston, the wiper, I, strikes the rocker, Gr, andthus causes the movable seat to travel along with the valveand therebyto keep a communication between the cavity, m, and port, a, in anoblique direction through the port a*, as will be seen by examining thethe relative positions of the valve and movable seat shown in redoutline. When the valve has arrived in the position shown in red outlineand passed the edge, z', of the port, a, in the fixed seat, the lead hascommenced for/induction through the said port,

a', and consequently it is timeefor the Wiper, I, to escape over therocker, G, to let the seat be thrown back by the spring, f, to theposition shown in black outline which opens one communication from thesteam chest through the ports, a*, into the port, a, and another fromthe port, a, through the port, al, into the cavity m. During themovement of the valve in the opposite direction, the'vviper, I, actsupon the rocker, G, in a similar manner, only in the opposite direction,and the -operation of the ports, a, a*, are relatively the same as theabove described operations of a', a*, while the operation of a', a*, arerelatively the same as the above described operations of, a, a*. VI donot confine myself to the particular mechanism herein described forgiving the requisite movement of the movable seat, E, as this may bedone by various mechanical contrivances. I

What I claim as my invention, and desire to secure by Letters Patent,is-

The movable valve seat,E, arranged and operating substantially as hereindescribed, between the valve andthe usual stationary valve seat. A

JOHN F. ALLEN. Witnesses:

WM. TUsoH, JAMES F. BUCKLEY.

